A little while back I wrote an article about a recent study which largely blamed farmed Tilapia for the loss of native biodiversity in Fijian waterways. I have since received e-mails from Gerald Billings, the Head of Aquaculture at the Ministry of Fisheries and Forests in Fiji. He expressed his concern over the paper’s intent and subsequent findings. As a scientist, I believe strongly in impartiality, so I’ve posted the entirety of his response to the study after the fold for you to read if you wish. I don’t like the idea of supporting bickering between governments and conservation organizations, but in this case, I feel the need to comment more on this paper. Indeed, there are many sides to the story here, and my first pass was a little short-sighted.

I am a conservationist at heart, so I was clearly drawn to the message of the Tilapia study. I instantly agreed with the idea that our actions are having negative consequences in ways we haven’t even thought of, and that we need to be more careful when we throw species around the globe.

But, Mr. Billings brings up counter points to the study that cannot be ignored. Indeed, as he states, there is a growing need to feed people that cannot be met by the current native species, and the authors management plan does not include any way of dealing with this issue. To be fair (to myself), I did bring this up in my review. To quote myself on the issue (which is a very strange thing to do),

It’s a good plan for the native fish, but as the human populations continue to expand, countries like Fiji will, out of necessity, rely more and more heavily on compact, efficient means of producing food like fish farms. As they do so, it will be harder and harder to keep the fish in the farms from escaping and damaging the surrounding habitat. While this paper serves to warn of the downsides of aquaculture, it unfortunately doesn’t provide a solution to the underlying problem of too many mouths to feed on limited resources.

But Mr. Billings also brings up another valid point that I didn’t recognize the first time I read the study. It’s my age-old pet peeve, and this time, I failed to properly critique the authors: correlation isn’t causation.

The paper looked at a number of variables and correlated them to native fish density and diversity. To summarize the entire paper super-quickly, the researchers found that where tilapia lived, native fish didn’t. They suggested that this was due to tilapia’s voracious appetite. What they didn’t do is actually justify that position – they provided no data to show that tilapia introduction in a previously tilapia free waterway caused a drop in native fish density.

Mr. Billings is right: just because they’re at the scene of the crime doesn’t mean they committed it. Another perfectly plausible explanation for the correlation between tilapia presence and low native fish density is that, like many invasive and introduced species, tilapia is quick to fill ecological gaps. Instead of the tilapia eating their way through freshwater streams, it’s possible that some other disturbance created ecological holes that the fast-breeding, adaptable tilapia gladly filled.

That’s not to say that studies like this one shouldn’t be done: indeed, understanding what is happening in an ecosystem is the first step in understanding why it is happening. I still believe this paper is interesting and vital to understanding the role invasive species may play in ecosystem decay, but some of the authors’ conclusions must be taken with a grain of salt. At minimum, they must be supported by further research into the interaction of tilapia and native fish.

The Fisheries Department of the Ministry of Fisheries and Forests is very concerned at the numerous press coverage on radio and newspapers with specific concern at one recently published article in the Fiji Sun 30/01/10 where a group of so-called overseas and locally based scientists have solely blamed tilapia for ten other missing freshwater fish species.

The articles are seen as not only scientific propaganda but attempts to create a negative image of tilapia farming in Fiji, a Government based activity, designed to address food security in rural and semi-urban areas. This is particularly evident in their references of tilapia as “pig food” and “aquatic cockroaches”

The article imposes on two main issues, namely:

1. The threat to our local food sources and

2. The threat to our biodiversity by the so called invasiveness of tilapia in our waterways.

A regional meeting recently hosted by the Secretariat of the Pacific Community (SPC) in Noumea, New Caledonia in December, 2009, was called to address specific issues on the future of tilapia farming, not only in Fiji, but the Pacific. A co- author of the article, Dr. Aaron Jenkins also attended the meeting and was invited to present his research findings as mentioned in the latest article.

In doing so he came under a barrage of questions from leading professors and experts in the world who were present at that meeting who found the results shallow and inconclusive.

However, what emerged as the main theme of that consultation was that in many places, the environmental cost from past introductions of tilapia had already been paid, and what we now need to see is how best Pacific Islands can now responsibly obtain the expected social benefits?

On the threat to our local food sources the Pacific Islands will face an increasing shortfall in availability of fish for domestic consumption.

SPC analyses show that an additional 100,000 tonnes of fish will be needed by 2030, if present dietary levels are to be maintained.

Even assuming good management and no impacts on coral reefs by climate change, the region’s coastal fisheries will not be able to supply the fish needed.

On the one hand, farming of tilapia is one of the readiest available responses to regional food security concerns. On the other hand, tilapia is an introduced species that, we can all agree, raises concerns about impacts on indigenous freshwater fish biodiversity.

Small-scale fish farming requires a fish that is simple to breed and simple to feed, and the obvious choice is tilapia. There are no obvious candidates among the indigenous freshwater fishes in Fiji and in this region, and the gudgeon fish mentioned as being threatened in the report are only for the prestigious aquarium trade, not for providing any food security for our local population.

However, ninety per cent of the tilapia farmed globally and in Fiji nowadays is Nile tilapia, a much genetically improved and acceptable strain.

This variety is available for distribution to farmers and has been domesticated for pond conditions. We have been farming these for over a decade now and not only do they contain a much high protein, but are much larger and tastier than the earlier introduced species.

This fish provides the much needed protein food security for the poorer and rural communities that don’t have access to more expensive reef fishes, and secondly provides additional income that targets the requirements and specific demands of a growing Asian population in the country.

On the comment by the authors that “tilapia the aquatic chicken” be nicknamed “the aquatic cockroach” is irrational and insensitive to a large and indigenous sector of our local community that look forward to tilapia in their family meal.

It also undermines the alternative high and affordable protein food requirement available for our rural and semi-urban populations.

In the United States, tilapia is rated among the five most popular fish in restaurants and other food outlets and it now even rates higher than salmon fish, and this specific reference of tilapia as “aquatic cockroaches” by Dr. Stacy Jupiter may not be accepted lightly by her own American counterparts.

On the “threat to our biodiversity” mentioned in the article, there is a tendency at times for some environmental NGO’s to ingratiate themselves to local communities by clearing them of any blame for particular environmental outcomes, preferring instead to adopt a popularist strategy of blaming government sponsored programs and other external agents.

There are many other contributing factors that should have been considered in the survey methodology that are possible reasons for the absence of other fish that were not seen in the survey.

Indiscriminate tree-cutting, use of local duva (deris deris) and other chemicals (including chlorine as highlighted recently in a daily to catch land crabs (mana) are common practices in rural areas in such streams and waterways, although in defiance of Fisheries legislation banning their use for such activities.

In the use of such chemicals, all fish and fry are killed including gobies, gudgeons and tilapia alike, as there is no discrimination on what dies and what is allowed to live.

Flood mitigating dams that are now common the country over also prevents any internal migration especially for spawning purposes.

Indiscriminate logging practices are now commonly practiced in the hills and are difficult to monitor.

Blaming the symptom (tilapia) instead of the disease (poor land use management) will never get to the root cause of most biodiversity loss and only plays into the hands of real-estate developers and logging companies, who might be able to continue their destructive (and highly lucrative practices), while blaming tilapias for just doing what comes naturally.

Poverty and hunger are often major drivers of deforestation and unsustainable agricultural practices, further drive biodiversity towards extinction.

They can often be found at the scene of the crime, but are not necessarily the criminal.‘

Demand for fresh fish in Fiji and the region will increasingly drive new initiatives to farm and expand tilapia production through mass introductions to waterways that already have the fish.

There are over 300 existing farms in operation in Fiji and the demand for the fish is increasing daily at a very rapid pace.

Finally, to address the issues of missing biodiversity, zoning approaches have already been considered in aquaculture planning process to protect existing biodiversity.

This is considered the most favourable approach to protect areas of high conservation value from further introduction of tilapia, but if other indiscriminate practices are allowed to continue, this process will produce very little outcome.

In the meantime, aquaculture farming will continue. The issue here is that tilapia has already been introduced, and is here to stay.

The last line of the letter is the most important. The Tilapia are indeed there to stay. Here in Austin, a fellow told me the Tilapia in his lake died as a result of our recent unusually cold winter. Clearly, more work needs to be done on cold weather acclimatization. (sarcastic comment!) Given the history of Tilapia introductions, I think it ridiculous not to think they are responsible for environmental changes driving out native species.

“… dietary fish oil is required for the production of omega-3-rich farmed fish and this commodity, in a vicious circle, is at present derived solely from wild fisheries…. This review attempts to compile all principal information available regarding the effects of fish oil replacement for the diets of farmed finfish …. the production, availability and main nutritional characteristics of fish oil and the principal alternative lipid sources (such as vegetable oils and animal fats).”

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